The battle of Dhū Qār looms large in Muslim memories of pre-Islamic history. The early seventh century clash between warriors from the Arabian Bakr ibn Wāʾil tribal group and a Sasanian frontier force casts an especially portentous shadow into Islamic times since it is remembered as the first ‘Arab’ victory against ‘Persians’ and hence a foreshadowing of the Islamic Conquest of Iraq one generation later. Modern scholars note that classical-era Muslim writers inflated Dhū Qār’s significance when they viewed the pre-Islamic battle from the perspective of hindsight in post-conquest Iraq where the relative merits of ‘Arab’ vs. ‘Persian’ were disputed, but even deeper questions surround Dhū Qār’s legacy in Muslim memories which I investigate in this paper. I start by questioning the very ‘Arabness’ of the battle. The presence of self-styled ‘Arabs’ in post-conquest Iraq starkly contrasts the virtual absence of ‘Arabs’ in the pre-Islamic historical record: it appears that the early centuries of Islam were a fertile period for Arab ethnogenesis when various disparate pre-Islamic Arabian groups which later converted to Islam and participated in the Conquests were retrospectively amalgamated into a cohesive ‘Arab’ ethnos. Early Islamic history-telling thus involved the creation of an ‘Arab past’ to narrate a myth of origins for the post-conquest society, and Dhū Qār was a key landmark in that process. Poetry and anecdotes which coalesced around the story of Dhū Qār between the eighth and tenth centuries reveal the battle’s changing significations over time and indicate its status as a significant ‘lieu de mémoire’ in early Islam’s cultural memory. Like Pierre Nora identified contested memories surrounding diverse lieux de mémoire in modern-era constructions of the French national consciousness, the varied memories of Dhū Qār relate to shifting constructions of post-conquest Iraqi identities. Poets and narrators re-told and re-remembered the battle, gradually transforming it from a tribal conflict to a pivotal moment in Arab ‘collective memory’ and pendant piece to Islam’s greatest victory, Muḥammad’s battle at Badr. My diachronic textual analysis offers a window into the complex process by which Arab-Muslim identity was forged and illustrates how Muslims used the past to articulate the nexus of ‘Arab’ and ‘Islam’ in their ever-changing presents.